In my planned wifi booster set up, the antenna will be on an extending mast attached to the back bumper. The hotspot/router will be in the upper rear cabinet. That will be just a few feet away from the antenna.

I wonder if there might be interference or feedback between my hotspot/router and the antenna? I suspect this is not an issue, however, it would be nice to read some comments on the matter.

I wonder if there might be interference or feedback between my hotspot/router and the antenna?

This is certainly a valid concern with cellular network boosters, but a WiFi system is different.

It is assumed by the design of the WiFi standards that there will be multiple networks running in close proximity, and they manage coding and use of frequencies to avoid problems with collisions. Although the same data is moving through the campground's WiFi network and then your additional network, it does that as separate messages which each network handles by itself, not getting confused what is in the other network. The end result is just like having the local hotspot created by your mobile phone in the same room as hotspot for a network belonging to the home or business which you're in... no problem.

Cellular boosters are relatively crude by comparison. They receive signals from the cellular network on one antenna and blast it right back out again from a second antenna, so it can be received by the first antenna which has no way to understand that it is not a legitimate network signal. Sufficient isolation of the two antennas is necessary (although not a problem in reasonable installations).